The present invention relates to a new and improved construction of a machine for the strapping or wrapping of various types of articles or packages with a ligature, typically a wrapping or strapping band or strap.
Generally speaking, the package strapping machine of the present development is of the type wherein the strapping band has the starting portion thereof engaged by a carriage or traveler which is supported by an endless band or belt or equivalent carriage drive element. The starting band portion is guided by the moveable carriage about a prescribed band guide or travel path along a package strapping tunnel which receives the package or article which is to be tied with the strapping band, so that there can be formed a band strapping loop around the package from the thus guided strapping band. There are also provided holder means protruding into and moveable out of the plane containing the band strapping loop in order to retain such band strapping loop and to release such so that it engages about the package. There is also provided an intermediate band storage having a reverse or take-up storage capacity for taking-up slack of the strapping band, this intermediate storage being arranged between a band supply roll and the travel path of the strapping band. A clamping and connection device serves for fixedly retaining and connecting the ends of the strapping band which encircles the package.
Such type of package strapping machine which contains a band strapping tunnel and operates automatically in response to push-button actuation serves for the continuous wrapping or tying of successively infed packages or articles, which, for instance, can be constituted by the most various type of packages or objects which are to be wrapped with a wrapping or strapping band or the like or tied into package bundles. As the ligature or strapping band there is preferably employed a plastic band or strap which is paid-off a band supply roll and tightened about the package, cut and welded or heat-sealed at its ends so that such band ends are firmly interconnected. The ligature can, however, also possess a different cross-sectional configuration than that of a band or tape or a cord. The article or package strapping machine is particularly contemplated for use with ligatures or strapping bands or the like which, by virtue of their insufficient stiffness or rigidity, must be pulled or drawn about the package to be strapped or tied instead of being pushed thereabout.
A strapping machine of this type which is known from the German Patent Publication No. 2,518,211, possesses a program circuit for controlling the carriage or traveler, designated as an entrainment clamp or gripper, for the ligature. The stopping of the carriage as well as the operations required for transfer of the starting portion of the ligature trained about the article or package and for seizing the new ligature starting portion is controlled by means of a circuit. With this arrangement, it is necessary to stop and again accelerate the belt carrying the carriage in conjunction with the carriage following each orbit or revolving motion of the carriage. However, each acceleration requires an increased amount of time the greater the mass which must be accelerated. Furthermore, during each acceleration the parts which are accelerated are subjected to increased wear. In order to be able to rationally employ such strapping machine the working or operating cycle must be as brief as possible.
A further drawback of the heretofore known strapping machine is the return or band slack take-up force which is limited by the storage containing the return storage capacity during tensioning of the ligature about the package. This is governed by the fact that the band storage comprises a through-pass storage arranged between the supply roll and the band carry region, wherein the return or take-up force of such storage must be smaller than the tension force of the carriage.
Furthermore, there is known from the German Pat. No. 913,637 a strapping machine which, however, does not belong to the species of strapping machines classified as tunnel machines. Here, the articles or packages which are to be strapped or tied cannot be successively pushed through the machine. Consequently, it is necessary to laterally withdraw each strapped package towards that side where such package has been infed to the machine, whereby there is rendered more difficult a rational handling of the packages. This prior art machine possesses a chain which is continuously driven and equipped with projections serving as entrainment members. A dolly or carriage guided by rollers upon a guide track can be coupled with and decoupled from this chain. The dolly or carriage draws, by means of an eyelet-like device, a wire serving as the ligature about the previously inserted package. Owing to the manner of infeeding the ligature, this prior art machine is not suitable for the processing of bands. The circulating chain and the dolly or carriage traveling upon the rollers generate a great deal of noise. The entrainment members arranged at the chain require a special design of the chain which is subjected to wear and such not only generate additional noise upon coupling the dolly or carriage, but also there is present a jerk-like loading of all of the moveable parts. This prior art strapping machine also is not capable of accomplishing a preparatory loop formation, so that the band strapping or tying operation only can be accomplished after the insertion and retension of the package or article to be wrapped. Consequently, with this known machine there are not possible any appreciable short operating or work cycles.